This proposal seeks continuation of support for a Center Grant for a series of studies aimed at cancer prevention. The underlying philosophy is that where the causes (or enhancing factors) of cancer can be identified, means for control can be sought. In a similar way, identification of the underlying mechanisms involved in the conversion of a normal to a malignant cell may permit the development of means for interrupting that conversion, thereby preventing the development of malignancy. The program deals with chemical, physical and biological factors in the causation of cancer as well as their interaction. The approaches described cover a wide range and include biochemical studies of intracellular mechanisms including cell kinetics, the development of mathematical models for cancer induction, and epidemiological studies on human populations aimed at the identification of causal factors. Clearly, cancer prevention is a most desirable means of the control of cancer. It is believed that there are solid leads which promise practical results in the attainment of means for the prevention or reduction of some forms of cancer. The Center Grant would be used primarily for the core support (senior staff, key equipment and central services). The major supporting funds would be sought through the usual grant and contract sources.